Electric call-bell



(Model) 4 Sheets-Sheet 1. A. G. BELL.

Electric 0811 Bell.-

' No. 238,833. Patented March 15,1881.

. m i u? m s2 2 A Ll g 1. Inventor:

JW v N. PETERS, FHDTO-LITHOGFIAPHEIL WASHINGTON, D. C.

(Model.) 4 SheetsSh.eet 3.

V A. G." BELL. Electric; 0311 Bell.

No. 233,333. Patented Ma'rch 15,1881.v

m I ttuumm Fig.5.

Inventor: 3 M 7% JW Nil-215315, EHOYOMTHOGRAPHER, WASHINGTON. n' c.

(ModeL) 4 Sheets Shee t 4.

A. G. BELL. Electric Call Bell. No. 238,833. Patented March 15, I881.

Ground (Yen/Zia] @fce. L flnlial Office.

WtZhesse/s I Dawn/26w the end farthest from the central office throughtion on either side.

ward movement of the armatures, and in order that the effect of thecurrent used for operat- UNITED, STATES PATENT OFFICE.

ALEXANDER G. BELL, .OF WASHINGTON, DISTRICT OF COLUMBIA.

ELECTRIC CALL-BELL.

SPECIFICATION forming part of Letters Patent No. 238,833, dated March15, 1881.

Application filed March 13, 1880.

To all whom it may concern Be it known that I, ALEXANDER GRAHAM BELL, ofVVa shington, District of Columbia, have invented a new and usefulImprovement in Electric Bell-Calls, of which the following is aspecification.

This invention relates to call-bells or signalin g apparatus for use inelectrical or telephone systems, so that an operator at one station cancall or signal any one of a series of stations without disturbing theothers.

Heretot'ore various apparatus have been devised for this purpose, theparticular construction of which need not be here set forth. In suchapparatus as in the ordinary system in which all the bells are rung atthe same time, the electromagnet for operating the switch mechanism, oran alarm at each station, remains always in circuit, thus causing greatre sistance. This high resistance, which is very objectionable forobvious reasons, can by the present invention be avoided, for althoughanelectro-magnet, switch, or signaling apparatus is located at eachstation only one instrument at a time is in circuit. This result isaccomplished by means of electromagnetic switches, which, operatingsuccessively, cut out their magnets and complete the line to the nextstation. To receive the switch-magnets as they are cut out a second lineis used, by the passage of currents over which the magnets can bereturned to first line. In the normal condition of the system the secondline is completed through all the stations to ground, and can be used bythe way-stations or subscribers to call the terminal station or centraloffice. It is also sometimes used by the central office for calling asubscriber. Line No. l is normally divided into sections, each groundedat the magnet of the switch or signaling-instrument, and disconnectedfrom the adjoinin g sec- The first section is connected with the centraloffice. Telephone communication is had through line No. 1.

The electromagnetic switches best adapted for use as indicated operateto cut out their own magnets by the passage of a current through thecoils of the latter and by the for- (ModeL) ing one switch may notextend to the others, the adjoining or alternate switches are adapted tobe shifted by currents of opposite polarity.

In connection with electro-m agnetio switches as described bells areused, the hammers of which are or may be operated bythe same magnetsthat operate the switches. To do this efl'ectively the bells are adaptedto be set for ringing by a single rapid reversal of polarity of thecurrent. The particular means adapted for thispurpose are an improvedform of switch, and also other parts and combinations of devicescomprised in the present invention will be hereinafter more fully setforth.

In the drawings, Figure 1 is a plan, and Fig. 2 a rear elevation, of anelectrical-bell instrument adapted for the working of the principalfeature of my invention, and embodying some of its minor details. Fig.3is a side elevation,

and Fig. 4 a sectional elevation, of the same. Fig. 1* is a detail planview of a small port on of the apparatus. Figs. 5 to 12, inclusive, areviews, in detail, of certain parts or pieces used in the construction ofsaid instrument, as will be more particularly pointed out; Figs. 13 and14 are diagrams used in explanation of my said invent-ion.

Ais a metallic bed-plate, secured to'a wooden table, A, by screws .9.

P is a metallic plate, secured by screws 8 to the tops of three posts,0, which are fastened to the bed-plate, as shown. For convenience thisplate P is of peculiar shape, as shown in Figs. 5 and 6. In reartheplate P has two projections, b b. In front it has a slot, 0, throughwhich vibrates the arm h of the bell-hammer H, while through a branch,0, of said slot vibrates an arm, a, whose office will be hereinafterpointed out. In the branch 0 is a projection, y, the office of whichwill also be pointed out hereinafter.

F is a swinging armature, oi soft iron, pivoted at c 0, as shown, to theperpendicular arms of a yoke, G, which is secured to the bedplate byscrews 8 as shown. The arm 72. of the bell-hammer before mentioned isrigidly secured to the armature F, but it projects some distance belowthat armature, and near its lower end is provided with a pin, 01, uponwhich is pivoted, at its own lower end, a tongue, in. This tongue is apermanent magnet, and

forms a swinging polarized armature for the electro-magnet E, its upperend being between the adjustable pole-pieces p 9, attached to theprojecting ends of the cores of the two spools of the electro-magnet.

To the upper end of the polarized tongue or permanent magnet m issecured, as shown, the arm a, previously mentioned.

It will be at once observed that the permanent magnet m, andconsequently the arm or also, is capable of vibrating about axes atright angles to each other, and thus has a movement in fourdirectionsnamely, forward and back with the} armature F, and to eitherone side or the other at right angles to its forward and back motion.

That the polarized tongue m may retain its power there are placed inclose proximity to its lower end the ends of two strong permanentmagnets, M M, screwed to a piece of brass,

N, which, in turn, is secured to the bed-plate by screws 8 s underneath.

G G are two bell-crank levers pivoted to the plate P atff, their longarms being also pivoted to the rubber base I ofa sliding switch,

T. (Shown in detail at Figs. 10, 11, and 12,

Fig. 11 being an elevation and Fig. 12 a plan of said switch, while Fig.10 is a plan of the switch inverted.) The switch consists of the saidrubber base Z and six metallic plates, 6 e e e, underneath said base,and e and 6 above. These plates are secured to the base I by metallicpins, and through these pins plates 6 1 and e are in metallicconnection, and also 0 and 6 J is a rubber plate, secured to the lowersurface of the arms b l) of the plate P by screws, as shown. Through itare inserted three metallic pins, 72 n a, forming a support for theswitch T, in the nature of a tripod, so that all three pins are inconstant contact with the switch as a whole. The pin it is alwaysincontact either with plate 0 or 0 n always in contact either with e or e,and a always with e.

'T are the metallic points upon the ends of two -metallic springs, g 9the other ends of the In contact with th e upper plates of the switchsprings being secured to insulated posts q g by screws 0 0 The spring 9'is always in contact with either plate 6 or a, while 9 is always incontact with 0 Electric connection is made with the switch, as will behereinafter pointed out but itmay be here observed that there is apeculiar advantage in this form of construction of a switch and in itsimmediate connections as thus far described. Be-

ing flat and sliding horizontally the switch must at all times rest uponall three of the pins n n a below, and there is no strain upon theelasticity of the springs g above.

B, B B B and B are binding-screws upon the bed-plate, but, with theexception of B is in contact with the ground-wire. Wire w connectsbinding-screw B with screw 0.

'sition shown in Figs. 1 and 1 in full lines. View it not for thisforwardly-extendin g stop- Wire 10 connects pin a with binding-screw BWire w connects screw 0 with the electromagnet E. Wire w connects theelectro-magnet E, through the plate A, with the bindingscrew B that is,with the groundthe whole course of the wire, however, not being shown.Wire 20 connects binding-screw B with pin a, and wire w connects pin awith bindingscrew B.

D is a bracket screwed to the plate P, and having projections uponeither side of the branch slot 0, to furnish support for the free endsof the short arms of the bell-crank levers G G as they move in and out.These levers are operated by the arm a, attached to the polarized tongueor permanent magnet m. Their short arms are of such length that'they canbut just pass each other without striking in their movements in and out;and it is obvious, from description already given, that when one movesin the other moves out.

By having the operating or short arms of the levers G G extending towardand closely approaching each other, only a slight movement of thepolarized tongue is necessary in order that it maybe brought into therequired position to strike one or the other of said lever arms.

When the armature is drawn forward and the arm a strikes either of theleverarms, the latter is moved into contact with a stop-piece, no, onbracket D, and prevents the bell-hammer from reaching the bell. To ringthe hell it is necessary that the arm a should be swung around the endof the lever-arm, so as to be inside of the same, as shown by dottedlines, Fig. 1. Referring to this figure it will be seen that this can bedone by causing the armature to be attracted by acurrent of suchpolarity that the arm a will pass the end of the lever-arm G and then,by a single rapid re-, Versal of current, shifting the polarized tonguem (to which the arm a is attached) before the neutral armature has timeto fall back. The bell can now be operated as often as desired, so longas the polarized tongue remains in position. The hell can also be rungwith the lever-arms in the position shown in Fig. 1, the current firstused being that which will retain 1 15 the arm a in position to pass theend of lever G. I To restore the armature and polarized tongue to theposition for operating the switch-lever a current is sent of thepolarity opposite to' that by which the bell has been rung. During thepassage of the current the sidewise movement of the tongue is preventedby the stoppiece y; but when the armature falls back the tongue isreleased and moves over into the po- IIO piece 3 or its equivalent, thearm a, instead of being released, would be shifted behind the otherlever-arm.

The diagram in Fig. 13 illustrates the combination of a seriesofinstruments in a system with the lines of wires in their normalcondition. Line No. 1 extends from central office to binding-screw B atfirst station through the magnet of the instrument thereat to ground.The section of line between first and second stations is disconnectedfrom the central office section, and is grounded through the magnet ofthe instrument at second station. At each station there is a gap in theline, and the preceding section is grounded through the instrument onthat station. In other words, there are a series of grounded instrumentseach arranged in a disconnected section of the linewire.. Line No. 2iscompleted through all the stations and grounded at its farthest end. Inthis line is shown a series of circuit-breaking switches operated bypuslrknobs, by means of which and a battery and signaling-instrument atthe central office, any station may call the central office. in eachstation of line N o. 1, as it enters the switch and bell-instrument, isa telephone or telephonic apparatus of any ordinary or suitableconstruction, (shown as a hand telephone suspended from agravityswitch,) which short-circuits the telephones when not in use.

The operations of the instrument and a series of such instruments are asfollows:

First, taking a single instrument, let the battery be attached toline-wire No.1 and let the arm G be pushed in so that the plate 6 of theswitch T is in contact with both the springs g 9 This is the normalcondition of any instrument on line No. 1, and the current is frombinding-screw B, through wire 10, screw 0, spring g, plate 6", spring 9screw 0 wire m electromagnet E, and wire w, to ground. If, now, animpulse is sent through the line of such polarity that the polarizedtongue or magnet m is attracted (to the right in Fig.1 of drawings) sothat the arm a will in a forward motion strike the bell-crank lever G,the bell will not ring, and any number of such impulses may be sentwithout ringing the bell, for the arm of the bell-crank lever G,striking against the shoulder a: of the bracket I), in turn forms a stopto prevent the bellhammer from reaching the bell. For convenience wewill assume that the impulse sent was a impulse. The bell, however,might be rung by first sending in rapid succession a single followed bya single impulse, and then at leisure sending a impulse. This is becausethe arm of the bell-crank lever (l is drawn back, as shown in Fig. 1, inthe normal state of theinstrument, and by following the impulse by aimpulsebefore armature F has time to fall back, the arm a has given toit a motion to the left, Fig. 1, so that it passes around the end of thebell-crank leverG as already explained, and no longer prevents .thebell-hammer from reaching the bell.

Second, the instrument whose operation has been thus far described whenin its normal condition, can be sent 0% of line No. 1 by sending aimpulse. Such an impulse throws the polarized tongue m and arm a to theleft, Fig. 1, andat the same time the arm a. is carriediorward by. thesoft-iron armature and strikes the bell-crank lever G thus shifting theswitch T, when it will be found that the current is from binding-screwB, through wire to, screw 0, spring g, plate 6 plate 6, pin a wire 20 tobindin g-screw B thatis, the switch I is now connected with the line No.l at both ends-or, in other words, agap in line No. 1 is filled and thecurrent is no longer through the electro-magnet. This is the conditionof the instrument as shown in Figs. 1, 2, 3, 4, and

plus current, and the instrument may be" sent back to line No. 1 bysending a impulse over line No. 2, and on returning to line No.

1 the instrument will resume its normal condition.

Fifth, the normal condition of line No. 2, in connection with theapparatus, when the instrument is on line No. l is such that a currentupon it would pass from binding-screw B, through wire r0 pin a, plate 6.pin n wire 10", to binding-screw B, a gap in the line No. 2 betweenbinding-screws B B being thus filled.

Sixth, the bell of an instrument the polarity of whose permanent magnetdiffers from the polarity of the instrument just described, if placedupon line No. 1, will, it is obvious, not ring in its normal conditionif minus impulses are sent through it. It may, however, be rung bysending first a minus impulse and then rapidly reversing the polarity ofthe current. By sending asuccession of plus impulses the bell may now berung as often as desired. Such an instrument, when in itsnormalcondition upon line No. 1, may be. sent over to line No. 2 by a singleplus impulse, and returned to its normal condition on line No. 1 bytransferring the battery and sending a minus impulse over line No. 2.

Seventh, after one instrument on line 1 has been transferred to No. 2and the gap in the line filled by the passage of a current through theelectro-ma-gnet, the current, if continued on the line, will pass to thenext instrument, and itlthe latter is in all respects, both inconstruction and connection, the same as the first instrument, it willbe shifted to line No. 2. In order to avoid this difficnlty theadjoining or alternate instruments are adapted to be operated bycurrents of opposite polarity. This, it is evident, can be effected by achange in the connections of the line-wires; but more advantageously byhaving the tongues or magnets m of adjoining or alternate instruments ofopposite polarity. The passage of a negative current, by which the firstinstrument has IIO been shifted to line No. 2, will not operate eitherthe switch or bell, as the polarized tongue will be held in position tostrikelever G when the neutral armature is attracted.

Eighth, it follows, from the foregoing description, that any number ofinstruments may be arranged upon a line and operated successively; thatby using a second line, as indicated, the magnets of the instrumentsmaybe shifted from one line to the other, and that any instrument mayberung from the central office without ringing any other. This will,perhaps, be more readily understood by an examination of Figs. 13 and14, which represent my invention as worked with five instruments. Inthese figures it is shown, and it is in accordance with the previousdescription, that whenever the instrument is on either line the currentof that line is grounded in that instrument, and it then appears, as hasbeen stated, that when an instrument is transferred from one line to theother the gap is filled in the line abandoned. When, therefore, aninstrument is switched oil from line No. 1, an instrument behind theinstrument so switched off may be operated to ring its hell on the sameline No. 1, ormay, in turn, be switched off to bring in a thirdinstrument. By reversing the polarity of alternate instruments theliability of a second instrument to pass over to line No. 2 by animpulse imparted to the instrument lying before it is obviated.Accordingly in the diagram, Fig. 13, five instruments are represented intheir normal condition havingalternate polarities. The bell ofinstrument No. 1 might be rung by sending rapidly and then but it beingrequired to ring the bell No. 2 a impulse will send instrument No. 1over to line No. 2, when the bell of instrument No. 2 maybe rung bysending rapidly and then and it being required to ring the bell ofinstrument No 3, the condition shown in diagram Fig. 14, No. 1instrument will be switched off by a in]- pulse, No. 2 instrument byimpulse, and then the bell of No. 3 may be rung as if it were the No. 1bell. To now restore both lines to their normal condition, send a singleimpulse, which will restore instrument No.3 to its normal condition, andthen transfer the battery at the central ottice to line No. 2, and senda lmpulse, restoring instrument No. 1 to its normal condition, inconnection with line No. 1., and then send a impulse,restoringinstrument No. 2.

The switch mechanism above described, in connection with two main linesof wire, will be of great advantage for use in telephonic circuits; andthe principal object of the invention is that it may be so used. InFigs. 13 and 14, therefore, telephones are shown at each station in line1 as it enters the signal-instrument and push-button in line 2.

To illustrate the operation of a system thus constructed, let it besupposed that a person at the fifth or last station wishes tocommunicate with one at the third station. He first calls the centraloffice by means of his pushbutton, and indicates his number. Then theoperator at central office shifts the instruments scriatt'm to line 2until there is a clear line extending to and grounded through the laststation, and rings the bell to show that the call is heard. By means ofthe telephones the desire of No. 5 to talk with No. 3 is communicated tothe central office. The operator thereat then shifts instruments atfirst and second stations to line 1, rings thebell of No. 3 on line 2,shifts the instruments of Nos. 1 and 2 back to line 2, and, by means oftelephone, informs No. 3 that No. 5 wishes to communicate with him. No.5 could, by means of his pushknob, have indicated that he wished to beput in communication with No. 3, and in that case No. 3 would have beencalled by the central office first, and then the line completed to No.5.

It is evident that a secresy-switch of ordinary or suitable constructioncould be used if desired, and also a switch for cutting out thebeILmagnet when the telephone is in use.

It is preferred to use line No. 1 only for telephonic communication; butit is obvious that by placing the telephones at the stations in theground-wires, they, as well as the signaling-instruments, would beshifted from one line to the other, and that a station could be put withperfect secrecy in communication with the central office by either line.

For use in connection with the foregoing system l have devised anapparatus for the central office, whereby the necessary operations maybe performed quickly and with certainty. Such apparatus will, however,constitute the basis of a separate application.

Having thus explained the said invention and the manner in which thesame is or may be carried into effect, what I claim, and desire tosecure by Letters Patent, is-- 1. In a line-wire emanating from acentral office, a series of electro-magnetic switches arranged insections of said line-wire normally grounded through the switches, anddisconnected each from the section beyond, the several switchesoperating SGMtttiM each to disconnect its own magnet and ground-wirefrom the line and to close the break between its own and the succeedingsection, substantially as described.

2. In a line-wire emanating from a central office, a series of groundedelectro-magnetic switches arranged in normally disconnected sections ofsaid line-wire, and each operating to close the break between its ownand the succeeding section, the adjoining switches in said series beingoperated by currents of opposite polarity, substantially as described.

3. The combination, with an electro-magnet and switch operated thereby,of contacts and connections for completing a circuit through theelectro-magnet from either of two lines, according to the position ofthe switch, substantially as described.

4. In an electric circuit or telephone-line, a series of electromagneticswitches operating to disconnect from the line or throw out of circuitthe resistance of the coils of said magnet, substantially as described.

5. The combination, with two lines, of a series of electro-magnets,switches operated by said magnets, and contacts and connections wherebysaid magnets may be transferred, by means of electric currents, from oneline to the other, substantially as described.

6. An electrical system comprising a series of grounded electro-magnetic switches arranged in normally-disconnected sections of alinewire, a second line-wire, and contacts and connections for saidswitches, substantially as described.

7. Two line-wires, in combination with a series of electromagneticswitches acting to shift their magnets from one line to the other,substantially as described, adjoining switches being operated bycurrents of opposite polarity.

8. An electric bell adapted to be set for ringing by a single rapidreversal of current, and comprising an obstruction capable of preventingthe bell-hammer from reaching the bell in the normal position of theapparatus, which obstruction is cleared or rendered inoperative toprevent contact of the bell-hammer with the bell by means of the rapidreversal of current aforesaid, substantially as described.

9. The combination, in an electric hell or signaling-instrument, with apolarized armature controlling the operation of said bell or instrument,and pivoted, as indicated, of a projection around which the armature oran arm attached thereto is swung by a current of one polarity, rapidlyfollowed by one of opposite polarity, substantially as described.

10. The combination, with the projecting arm of a switch-lever, of apolarized tongue or armature capable of vibrating about axes at an anglewith each other, substantially as described, so that, according to thecharacter of the currents used, said tongue or an arm attached theretomay be caused to strike and operate said switch, or may be swung aroundit, as and for the purposes set forth.

11. The combination, with two switch-1evers having arms extending towardeach other, of a polarized tongue pivoted to the armature of anelectro-magnet and operating substantially as described.

12. The combination, with an electromagnet and armature, and bell-hammeroperated by said armature, of a switch-lever and stoppieces,substantially as described, said lever acting to operate a switch, andalso serving as a stop to the bell-hammer.

13. An electric switch having a horizontal motion only and resting uponthree contactpoints, substantially as described.

14. A horizontal movingelectric switch resting upon threecontact-points, having contactsprings above, without strain upon theelasticity of the latter, substantially as described.

15. The combination, with a polarized tongue pivoted to the armature ofan electro-magnet so as to vibrate across the plane of movement of saidarmature, of a stop-piece projecting toward said armature and adapted toprevent the movement of said tongue while the arma 7o ture is drawnforward.

16. The stop y, in connection with a horizontal moving electric switchoperated by two bell-crank levers, which, in turn, are operated by anarm having four motions derived from 7 the two armatures of anelectro-magnet, substantially as described, for the purpose specifled.

17. The combination, with an electro-magnet, armature, and polarizedtongue pivoted to said armature, of a switch and bell operated by saidmagnet, and contacts and connections whereby said magnet can be made toform part of either of two line-wires, accordin g to the position of theswitch, substantially as described.

18. In combination with two lines of wire and a telephone or telephonesat the central station, a series of signal-instruments, each instrumentcontaining a telephone and a switch, 0

the latter constructed substantially as described, and operated by anelectro-magnet and two armatures, one polarized and the other neutral.

19. The bell B, belLhammer H, soft-iron ar- 5 fication in presence oftwo subscribing wit- 10o nesses.

ALEXANDER GRAHAM BELL.

Witnesses:

PHILIP MAURO, O. J. HEDRIOK.

